1. Field of the Invention
The present invention pertains to a housing for an electric motor having a construction that is optimized to provide cooling for the electric motor. In particular, the present invention pertains to an electric motor housing having vent holes that are positioned and sized to increase a total air flow rate through the housing, an end wall of the housing that is shaped to conform to the stator winding end turns of the motor to optimize cooling of the end turns, and exhaust openings and an exhaust fan that are positioned and configured to improve air flow through the interior of the motor housing and into the fan.
2. Description of the Related Art
In home appliances, the size of an electric motor employed in powering the home appliance is often dictated by the size of the appliance and the area in the home that is designed to accommodate the appliance. For example, in many customized kitchens of homes today the kitchen counters and cabinets are designed with a spacing within the cabinets and beneath the countertop provided to accommodate the home dishwasher. The size of the spacing is primarily dictated by an acceptable kitchen counter height. When considering that it is desirable to have the interior of the home dishwasher be as large as possible to accommodate as many dishes, pots and pans, etc. as possible, the remaining interior volume of the dishwasher left to accommodate the water piping, electrical controls and electric motor of the dishwasher is very limited.
In looking to improve the performance of a home appliance such as a dishwasher, one of the first considerations is to increase the power of the water pump that produces the pressure behind the water jets of the dishwasher. This involves an increase in the size of the motor that drives the pump. However, increasing the size of an electric motor that is confined to a very limited area in the interior of the appliance often leads to problems in adequately cooling the motor. To address this problem, the housing of the electric motor and its exhaust or cooling fan should be specifically designed in order to optimize the rate of air flow through the motor housing and thereby optimize the cooling of the motor contained in the housing.
The present invention provides a housing construction for an electric motor and an exhaust or cooling fan for the electric motor that are specifically designed to optimize the rate of air flow through the interior of the motor housing and the cooling of the electric motor.
The construction of the electric motor itself is conventional. The motor includes a shaft having a center axis that defines mutually perpendicular axial and radial directions relative to the motor. A pair of bearing assemblies are mounted on the shaft and a rotor assembly is mounted on the shaft intermediate to the bearing assemblies. The rotor is received in the center bore of a stator assembly. The stator assembly has a laminate core surrounding the rotor and a plurality of windings with end turns of the windings projecting axially from the opposite ends of the core. The novel features of the invention are provided on the housing that encloses the motor and on a cooling or exhaust fan mounted on the shaft of the motor.
The motor housing of the invention is basically comprised of a first circular end wall and a second circular end wall that are axially spaced from each other by a cylindrical side wall that extends between the first and second end walls. Together the first and second end walls and the side wall enclose the electric motor in an interior volume of the housing. In the preferred embodiment, the second end wall and the side wall are formed as a single unit. The first end wall has a peripheral edge that is connected to an annular open end of the side wall. The second end wall has an annular collar on its interior surface that receives one of the bearing assemblies mounted on the motor shaft. The first end wall has a shaft opening that receives the second bearing assembly mounted on the motor shaft. A distal end of the motor shaft projects from the shaft opening.
A plurality of inlet vent holes arranged in a circular pattern extend through the second end wall adjacent the outer periphery of the stator winding end turns at that end of the motor. The vent holes pass through the second end wall adjacent the outer periphery of the end wall and continue axially for a length along the side wall of the housing. The area of each vent hole that passes through the housing side wall is larger than the area of each vent hole that passes through the housing second end wall. The shape and positioning of the vent holes optimizes the ingress of air flow into the housing in the area of the motor winding end turns.
The housing side wall is dimensioned to be slightly larger than the stator core providing an annular void in the housing interior between the exterior of the stator core and the interior surface of the side wall. A plurality of ribs extend axially over the side wall interior surface and project radially into the housing interior and engage with the stator exterior surface. The ribs hold the stator in the housing interior and define axial cooling channels between the ribs that are aligned with the inlet vent holes. The annular void between the stator core and the side wall provides a plurality of flow paths through the rib channels for cooling air received into the housing interior through the inlet vent holes.
The first end wall has an annular, concave interior surface. The interior surface closely follows the shape of the stator winding end turns as it extends radially inwardly from the periphery of the first end wall toward the shaft hole at the center of the end wall. This configuration of the first end wall interior surface channels the flow of air from between the stator and the side wall interior surface around the stator winding end turns to optimize cooling of the end turns. The first end wall is also formed with a recessed cavity in its exterior surface. A plurality of outlet vent holes pass through the first end wall in the recessed cavity. The outlet vent holes are arranged in a circle that is smaller than the circle defined by the plurality of inlet vent holes. The plurality of outlet vent holes are also surrounded by the annular, concave interior surface of the first end wall and receive the flow of air channeled around the stator winding end turns by the first end wall interior surface.
The fan is mounted on the distal end of the motor shaft that projects from the shaft opening of the first end wall. The fan has a cylindrical hub mounted to the shaft distal end and a plurality of blades that radiate outwardly from the center hub. Each of the blades has an inner end that is connected with the fan hub and an outer end adjacent to the outer periphery of the first end wall.
The construction of the motor housing optimizes the cooling of the electric motor contained in the housing. Operation of the motor rotates the fan which draws cooling air into the motor housing interior through the inlet vent holes. The larger portions of the inlet vent holes that pass through the housing side wall expose a large portion of the stator winding end turns to the cooling air that enters into the housing interior through the inlet vent holes. The annular void between the exterior of the stator core and the interior surface of the housing side wall and the plurality of axial ribs arranged around the interior surface between the inlet vent holes channel the cooling air over the exterior of the stator core to the axially opposite set of stator winding end turns adjacent the housing first end wall. The annular, concave interior surface of the first end wall directs the flow of cooling air around the stator winding end turns adjacent the housing first end wall and to the outlet vent holes surrounding the center of the housing first end wall. The fan blades draw the cooling air directed through the housing interior out through the outlet vent holes and pushes the exhausted cooling air radially outwardly across the exterior surface of the housing first end wall. Thus, the construction of the electric motor housing described above directs a greater rate of air flow across a greater area of the stator winding end turns and stator core of the electric motor and thereby optimizes cooling of the motor.